how to rotate a gameobject between two angles front and back direction?

Hello every one,

I am learn of Unity 5.4 and I am using visualstudio 2010 for coding. my coding is in C#.

I am trying to create a game object which is continuously rotating front and back direction in between two different angles.my problem is I am able to rotate the game object between origin to other angle successfully but I want to rotate it in between 60 -150 degrees.

below is the code for rotating between origin to any other angle. using UnityEngine; using System.Collections;

 public class turret1 : MonoBehaviour {
 
     
     public float rotF1;
     
     void Update ()
     {
 
         transform.localEulerAngles = new Vector3(0, 0, Mathf.PingPong(Time.time * 50, rotF1));
 
          
     }

thanks, malika.